1. Field of the Invention
The invention relates to an article comprising a pouch of a polyolefin film containing a solid alkaline or alkaline earth metal hydroxide, particularly a lithium hydroxide composition for use in the preparation of lubricating greases.
2. Description of the Prior Art
Lithium complex soaps used as thickening agents for lubricating greases can be prepared by reacting lithium hydroxide monohydrate or other lithium base with aliphatic monocarboxylic and/or dicarboxylic acids which may be saturated or unsaturated, straight or branched chain, and may be hydroxy substituted. Preferably, these acids contain about 6 to 30 carbon atoms and more preferably, from about 6 to 18 carbon atoms. It has long been known that a grease comprising a lithium soap of hydrogenated castor oil, or the lithium soap of 12-hydroxy stearic acid provide greases with exceedingly high mechanical stability and excellent water resistance.
In general, any of the conventional lubricating oils such as mineral, animal, vegetable or synthetic lubrication oils, may be employed as the grease base stock. These lubricating oils have a viscosity in the range of about 35 to 200 SSU at 210.degree. F. Mixtures of lubricating oils may also be effectively utilized. The grease compositions will usually contain about 70 to 95 weight percent, preferably about 80 to 95 weight percent, based on the total grease of the lubricating oil base. The lithium soap content may range from about 5 to 30 weight percent, preferably about 8 to 40 weight percent based on the total grease composition.
Lithium greases may be prepared as follows. The 12-hydroxy stearic acid or hydrogenated castor oil is dissolved in lubricating oil while heating to about 125 to 175.degree. F. at atmospheric pressure. Lithium hydroxide is added to this solution at about 180-190.degree. F., in a stoichiometric amount for complete saponification of the 12-hydroxy stearic acid and to provide a mixture of the lubrication oil and lithium complex soap; heating the mixture until it is uniform at a temperature from about 350.degree. F. to 430.degree. F.; rapidly cooling the mixture to about 300.degree. F. or below by quenching with additional lubricating oil and finally incorporating the remainder of the lubricating oil into the grease composition.
Lithium hydroxide is typically available commercially as the solid monohydrate (Li OH H.sub.2 O). This solid produces a dust when handled which causes choking and is extremely irritating, even in trace amounts. Anhydrous lithium hydroxide is especially dusty and more expensive to produce. Large amounts of lithium hydroxide monohydrate are used, as described above, in lithium grease manufacturing and the irritating dust is an environmental hazard during handling and mixing operations. Bulk powders of lithium hydroxide monohydrate can easily be spilled by the user, causing waste, as well as possible respiratory irritation. Furthermore, waste can also occur while loading the reactor through spillage, resulting in an insufficient charge, yielding a grease composition below the desired specifications. The granules or powders of lithium hydroxide monohydrate or anhydrous lithium hydroxide also have a tendency to clump and cake after contact with water or when stored in areas of high humidity. This caking diminishes the amount of exposed surface area which can be initially contacted by the lubricating oil base stock during the saponification reaction; thereby slowing the reaction. This caking of the lithium hydroxide thus interferes with dispensing efficiency.
Therefore, a need exists for lithium hydroxide granules or powders to be handled without exposing the user to safety hazards as through dusting, inhalation and spillage.